if you try to output massive amounts of texts it will either cut of the text at about 8ooo characters (for reasonable massive strings, < 32 K characters) or (for insanely massive strings, about 1.6 million characters) totally crash without even throwing an error or anything (I even put it in a try/catch without getting any result from the catch).

I had this problem when I tried to debug a response from a wp_remote_get(); all of my error_log() worked as they should, except for ONE of them... (-_-)After about a day of debugging I finally found out why & that's why I type this.

Apparently the response contained a body with over 1.6 million chars (or bytes? (whatever strlen() returns)).

Beware! If multiple scripts share the same log file, but run as different users, whichever script logs an error first owns the file, and calls to error_log() run as a different user will fail *silently*!

Nothing more frustrating than trying to figure out why all your error_log calls aren't actually writing, than to find it was due to a *silent* permission denied error!

It appears that the system log = stderr if you are running PHP from the command line, and that often stderr = stdout. This means that if you are using a custom error to both display the error and log it to syslog, then a command-line user will see the same error reported twice.

when using error_log to send email, not all elements of an extra_headers string are handled the same way. "From: " and "Reply-To: " header values will replace the default header values. "Subject: " header values won't: they are *added* to the mail header but don't replace the default, leading to mail messages with two Subject fields.

Note that since typical email is unencrypted, sending data about your errors over email using this function could be considered a security risk. How much of a risk it is depends on how much and what type of information you are sending, but the mere act of sending an email when something happens (even if it cannot be read) could itself imply to a sophisticated hacker observing your site over time that they have managed to cause an error.

Of course, security through obscurity is the weakest kind of security, as most open source supporters will agree. This is just something that you should keep in mind.

And of course, whatever you do, make sure that such emails don't contain sensitive user data.

When logging to apache on windows, both error_log and also trigger_error result in an apache status of error on the front of the message. This is bad if all you want to do is log information. However you can simply log to stderr however you will have to do all message assembly:

In the case of missing your entries in the error_log file:When you use error_log in a script that does not produce any output, which means that you cannot see anything during the execution of the script, and when you wonder why there are no error_log entries produced in your error_log file, the reasons can be:- you did not configure error_log output in php.ini- the script has a syntax error and did therefore not execute

After scouring the internet for getting event logging to work in syslog on Windows 2003, I found the following from this post and was able to successfully get Windows Event Viewer to log PHP errors/notices:

1. Copy the PHP 5 binaries to "C:\php". 2. Right-click My Computer and select Properties to bring up the Computer Properties dialog. Switch to the Advanced tab and click Environment Variables. Find the system environment variable PATH, edit it and add ";C:\php" (without the quotes) to the end. 3. Make sure that the configuration file "php.ini" resides in the directory "C:\php" and contains the correct path settings. 4. DELETE any old "php.ini" files from "C:\WINDOWS" and other directories. 5. Open REGEDIT, navigate to the key "HKLM\SOFTWARE\PHP" and DELETE the string value "IniFilePath" from there. It is outdated and no longer necessary! 6. Modify NTFS security permissions of the directory "C:\php" to give Read and Execute permissions to (1) the IIS Guest Account and (2) the group IIS_WPG. 7. Modify NTFS security permissions of the directories "C:\php\session" and "C:\php\upload" to give additional Modify permissions to (1) the IIS Guest Account and (2) the group IIS_WPG. 8. Navigate to the registry key "HKLM\SYSTEM\CurrentControlSet\Services\Eventlog\Application" and edit the value "CustomSD" there. Find the substring "(D;;0xf0007;;;BG)" which Denies access to the application event log for Builtin Guest accounts (like the IIS Web User account) and replace this substring with "(A;;0x3;;;BG)" which allows read and write access. Please pay attention to leave the rest of the security string intact. Damaging this value can have dangerous effects! 9. Create or update the registry key "HKLM\SYSTEM\CurrentControlSet\Services\Eventlog\Application\PHP-5.2.0" (adapt the last to your version part if necessary) with the following values: